Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

An illumination device includes: an excitation light source that emits
excitation light having a first wavelength; and a fluorescent member that
includes a fluorescent substance that, when it is irradiated with the
excitation light, emits light having a second wavelength longer than the
first wavelength, transmits a part of the excitation light and reflects
another part of the excitation light, and a first reflective film
provided at a side of the fluorescent substance, which is opposite to an
excitation light incidence side, the fluorescent member emitting
multiplexed light including an excitation light component reflected from
the fluorescent substance and the first reflective film and a light
component emitted from the fluorescent substance.

Claims:

1. An illumination device comprising: an excitation light source that
emits excitation light having a first wavelength; and a fluorescent
member that includes a fluorescent substance that, when it is irradiated
with the excitation light, emits light having a second wavelength longer
than the first wavelength, transmits a part of the excitation light and
reflects another part of the excitation light, and a first reflective
film provided at a side of the fluorescent substance, which is opposite
to an excitation light incidence side, the fluorescent member emitting
multiplexed light including an excitation light component reflected from
the fluorescent substance and the first reflective film and a light
component emitted from the fluorescent substance.

2. The illumination device according to claim 1, further comprising: a
spectral optical system that is provided at the excitation light
incidence side of the fluorescent member, the excitation light emitted
from the excitation light source and the multiplexed light emitted from
the fluorescent member being incident thereto, and that separates the
incident excitation light and the multiplexed light and emits them.

3. The illumination device according to claim 2, wherein the excitation
light is linearly polarized light, and the spectral optical system
includes a polarization beam splitter.

4. The illumination device according to claim 3, further comprising: a
quarter wavelength plate provided between the polarization beam splitter
and the fluorescent member.

5. The illumination device according to claim 2, wherein the spectral
optical system includes a base that transmits the multiplexed light, and
a second reflective film that is provided at a partial region of the
base, which includes an illumination position of the excitation light,
reflects the excitation light, and guides it to the fluorescent member.

6. The illumination device according to claim 1, further comprising: a
driving unit that changes an illumination position of excitation light in
the fluorescent substance with an passage of time.

7. The illumination device according to claim 1, further comprising: an
optical system that converts the multiplexed light emitted from the
fluorescent member into parallel light.

8. The illumination device according to claim 1, wherein the first
wavelength is a blue light wavelength and the second wavelength is a
wavelength band including red light and green light.

9. An image display apparatus comprising: a light source device section;
and an image projection section that generates a predetermined image
light by using multiplexed light emitted from the light source device
section and projects the generated image light to the outside, wherein
the light source device section includes an excitation light source that
emits excitation light having a first wavelength, and a fluorescent
member that includes a fluorescent substance that, when it is irradiated
with the excitation light, emits light having a second wavelength longer
than the first wavelength, transmits a part of the excitation light and
reflects another part of the excitation light, and a first reflective
film provided at a side of the fluorescent substance, which is opposite
to an excitation light incidence side, the fluorescent member emitting
multiplexed light including an excitation light component reflected from
the fluorescent substance and the first reflective film and a light
component emitted from the fluorescent substance.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority from Japanese Patent
Application No. JP 2010-139175 filed in the Japanese Patent Office on
Jun. 18, 2010, the entire content of which is incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to an illumination device and an image
display apparatus, and more particularly, to an illumination device used
as a light source of a projection type image display apparatus such as a
projector, and an image display apparatus including the illumination
device.

[0004] 2. Description of the Related Art

[0005] In recent years, in regard to watching movies at home, a
presentation at a meeting, or the like, the opportunities to use a
projection-type image display apparatus, such as a projector, have been
increasing. In such a projector, as a light source, for example, a
discharge type lamp, such as mercury lamp, having a high brightness is
generally used. In addition, with the recent progress in the development
techniques for solid-state light emitting devices (for example,
semiconductor lasers, light emitting diodes, or the like), there has been
also suggested a projector using the solid-state light emitting device
(for example, see JP-A-2010-86815).

[0006] The projector disclosed in JP-A-2010-86815 is a DLP (Digital Light
Processing: registered trademark) type projector. In such a type of
projector, images are displayed in full color through a time division
display of approximately several thousand times per second for the
different colors. Therefore, in the projector of JP-A-2010-86815, a red
color light-emitting device, a green color light emitting device, and a
blue color light emitting device those utilizing the solid-state light
emitting device are separately prepared, and emitted light from each
light-emitting device is time-divisionally controlled, and is emitted to
the outside to display image light.

[0007] In addition, each of the light emitting devices, which are used in
the projector of JP-A-2010-86815, includes a light emitting wheel that is
rotatably driven, a light emitting material that is formed on a surface
of the light emitting wheel and absorbs excitation light and emits light
of a predetermined color, and an excitation light source (solid-state
light emitting device) that emits excitation light. In addition, as the
excitation light source used in each of the light emitting devices, a
light source that emits excitation light with a wavelength band shorter
than that of light emitted from the light emitting material is used.

SUMMARY OF THE INVENTION

[0008] As described above, a projector not using a mercury lamp has been
suggested in the related art, and in such a projector, it is possible to
realize a mercury-free projector in response to recent environment
problems. In addition, in a case where for example, a solid-state light
emitting device such as a semiconductor laser and a light-emitting diode
is used as a light source, it has an advantage that durability is longer
and a decrease in brightness is also lower compared to a mercury lamp.

[0009] However, the technique suggested in JP-A-2010-86815 is only
applicable to a light source device (illumination device), for example, a
DLP (registered trademark) type projector or the like that
time-divisionally emits plural kinds of single color light having
wavelengths differing from each other. The technology suggested in
JP-A-2010-86815 may be not applicable to application where a light source
device emitting white light is necessary, like an image display device
such as a 3 LCD (Light Crystal Display) type projector or the like.

[0010] Thus, it is desirable to provide a mercury-free illumination device
that is also applicable to various applications such as a 3 LCD type
projector and an image display apparatus having the illumination device.

[0011] An illumination device according to an embodiment of the invention
includes an excitation light source that emits excitation light having a
first wavelength and a fluorescent member. The fluorescent member
includes a fluorescent substance that, when it is irradiated with the
excitation light, emits light having a second wavelength longer than the
first wavelength, transmits a part of the excitation light and reflects
another part of the excitation light, and a first reflective film
provided at a side of the fluorescent substance, which is opposite to an
excitation light incidence side. The fluorescent member emits multiplexed
light including an excitation light component reflected from the
fluorescent substance and the first reflective film, and a light
component emitted from the fluorescent substance. In addition, the
above-described "wavelength" means a wavelength including not only a
single wavelength but also a predetermined wavelength band.

[0012] In addition, an image display apparatus according to another
embodiment of the invention includes a light source device section and an
image projection section, and a function of each section is as follows.
The light source device section has substantially the same configuration
as that of the illumination device according to the embodiment of the
invention. The image projection section generates a predetermined image
light by using the multiplexed light emitted from the light source device
section and projects the generated image light to the outside.

[0013] According to the embodiment of the invention, the illumination
device (light source device section) emits the multiplexed light
including the excitation light with a second wavelength that is emitted
from the fluorescent substance and a part of the excitation light with a
first wavelength that is reflected from the fluorescent substance and the
first reflective film. That is, according to the embodiment of the
invention, light having a wavelength band different from that of the
excitation light and the emission light is emitted. Therefore, according
to the embodiment of the invention, in a case where the excitation light
is set as blue light and the emission light is set as light (for example,
yellow light or the like) including both red light and green light, it is
possible to emit white light from the illumination device (light source
device section).

[0014] As described above, in the illumination device (light source device
section) according to the embodiment of the invention, it is possible to
emit light having a wavelength band different from that of the excitation
light and the emission light, and by appropriately setting a combination
of the first wavelength of the excitation light and the second wavelength
of the emission light, it is possible to emit white light or the like.
Therefore, according to the embodiment of the invention, it is possible
to provide a mercury-free illumination device that is also applicable to
various applications such as a 3 LCD type projector and an image display
apparatus having the illumination device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a schematic block configuration diagram illustrating an
image display apparatus according to an embodiment of the invention;

[0016] FIGS. 2A to 2C are schematic configuration diagrams illustrating a
fluorescent member used for a light source device section (illumination
device);

[0017] FIG. 3 is a view illustrating a configuration example of a
reflective film used in a fluorescent member;

[0018] FIG. 4 is a view illustrating a spectral characteristic example of
a polarization beam splitter used in a light source device section
according to an embodiment of the invention;

[0019]FIG. 5 is a view illustrating an operation of the polarization beam
splitter;

[0020] FIG. 6 is a view illustrating a spectral characteristic of emitted
light of the light source device section (illumination device) according
to an embodiment of the invention; and

[0021]FIG. 7 is a view illustrating a configuration example of a spectral
optical system according a modified example 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, description will be given to an example of an
illumination device and an image display apparatus having the same
according to an embodiment of the invention with reference to
accompanying drawings in the following order. In addition, in this
embodiment, a 3 LCD type projector is described as an example of the
image display apparatus, but the invention is not limited thereto. The
invention may be applied to any image display apparatus where white light
is necessary and the same effect may be obtained.

[0029] FIG. 1 shows a configuration example of an image display apparatus
according to an embodiment of the invention. In FIG. 1, for simplicity of
explanation, only main portions that are operated when image light is
projected to the outside in the image display apparatus 10 of this
embodiment are mainly shown. In addition, in FIG. 1, a configuration
example of a 3 LCD type projector is shown, but the invention is not
limited thereto. The invention may be applied to a 3 LCD type projector
using a reflection-type LCD light modulation device.

[0030] The image display apparatus 10 includes a light source device
section 1 (illumination device) and an optical engine section 2 (image
projecting section). In addition, a configuration of the light source
device section 1 will be described later.

[0031] The optical engine section 2 optically processes light (white light
LW in this example) emitted from the light source device section 1 to
generate image light LI, and magnifies and projects the image light LI
to, for example, an external screen. The optical engine section 2
includes, for example, a spectral optical system 20, a 3 LCD optical
modulation device (hereinafter, referred to as "a first LCD panel 21 to
third LCD panel 23", respectively), a prism 24, and a projection optical
system 25. In addition, the configuration of the optical engine section 2
is not limited to an example shown in FIG. 1 and may be appropriately
changed, for example, according to usage or the like. For example,
various necessary optical devices may be appropriately disposed on an
optical path between each of components inside the optical engine section
2.

[0032] In addition, in the optical engine section 2 of this example, the
first and third LCD panels 21 and 23 are disposed with light emitting
surfaces thereof opposed to each other, and the second LCD panel 22 is
disposed in a direction orthogonal to an opposing direction of the first
and third LCD panels 21 and 23. The prism 24 is disposed at a region
encompassed by the first to third LCD panels 21 to 23. In addition, in
this example, the projection optical system 25 is disposed at a position
opposing a light emitting surface of the second LCD panel 22 with the
prism 24 interposed therebetween. In addition, the spectral optical
system 20 is provided at a light incident side of the first to third LCD
panels 21 to 23.

[0033] The spectral optical system 20 is configured by, for example, a
dichroic mirror, a reflective mirror or the like, disperses white light
LW incident from the light source device section 1 into blue light LB,
green light LG and red light LR and emits light of each wavelength
component to each corresponding LCD panel. In this example, the spectral
optical system 20 emits each of the dispersed blue light LB, green light
LG and red light LR to the first LCD panel 21, the second LCD panel 22
and the third LCD panel 23, respectively. In addition, in this
embodiment, in the spectral optical system 20, a polarization direction
of each wavelength component is adjusted to be a predetermined direction.

[0034] Each of the first to third LCD panels 21 to 23 is configured by a
transmissive LCD panel. Each of the LCD panels transmits or shields
(modulates) the incident light with a liquid crystal cell unit by
changing an arrangement of liquid crystal molecules enclosed in a liquid
crystal cell (not shown) on the basis of a driving signal supplied from a
panel drive section (not shown). Each of the LCD panels emits the
modulated light of a predetermined wavelength (modulated light) to the
prism 24.

[0035] The prism 24 multiplexes the modulated light of each wavelength
component incident from the first to third LCD panels 21 to 23,
respectively, and emits the multiplexed light, that is, image light LI to
the projection optical system 25.

[0036] The projection optical system 25 magnifies and projects the image
light incident from the prism 24 onto a display surface of, for example,
an external screen or the like.

[2. Configuration Example of Light Source Device Section 1]

[0037] Next, an internal configuration of the light source device section
1 of this embodiment will be described with reference to FIG. 1. The
light source device section 1 includes an excitation light source 11, a
polarization beam splitter 12 (a spectral optical system), a quarter
wavelength plate 13, a condensing optical system 14 (optical system), a
fluorescent member 15, and a motor 16 (driving unit).

[0038] In the light source device section 1 of this embodiment, a
reflective film 31 and a fluorescent layer 32, which are described later,
of the fluorescent member 15, the condensing optical system 14, the
quarter wavelength plate 13 and the polarization beam splitter 12 are
disposed on an optical path of emitted light from the fluorescent member
15 in this order from the fluorescent member 15 side. In addition, the
excitation light source 11 is disposed in a direction orthogonal to the
optical path of the emitted light from fluorescent member 15 and at a
location opposing one light incident surface of the polarization beam
splitter 12.

[0039] The excitation light source 11 is configured by a solid-state light
emitting device that emits light of a predetermined wavelength (a first
wavelength). In this example, as the excitation light source 11, a blue
laser emitting blue light (excitation light Bs) with a wavelength of 445
nm is used. In addition, excitation light Bs of linear polarization light
(S polarization light) is emitted from the excitation light source 11. In
addition, in this embodiment, a wavelength of the excitation light is set
to a wavelength shorter than that of light (hereinafter, referred to as
"emission light") emitted from the fluorescent layer 32 that is described
later, in the fluorescent member 15.

[0040] In addition, in a case where the excitation light source 11 is
configured by a blue laser, it may be configured to obtain excitation
light Bs with a predetermined output by one blue laser, and it may be
configured to multiplex emitted light from each of plural blue lasers and
obtain excitation light Bs with a predetermined output. In addition, a
wavelength of the blue light (excitation light Bs) is not limited to 445
nm, and it is possible to use any wavelength as long as the wavelength is
within a wavelength band of light called blue light.

[0041] The polarization beam splitter 12 (PBS) separates excitation light
Bs incident from the excitation light source and emitted light
(multiplexed light) incident from the fluorescent member 15.
Specifically, the polarization beam splitter 12 reflects the excitation
light Bs incident from the excitation light source 11 and emits the
reflected light to the fluorescent member 15 via the condensing optical
system 14. In addition, the polarization beam splitter 12 transmits light
emitted from the fluorescent member 15 and emits the transmitted light to
the spectral optical system 20 in the optical engine section 2.

[0042] In this embodiment, a spectral characteristic of the polarization
beam splitter 12 is designed to realize the above-described light
separating operation in the polarization beam splitter 12. In addition, a
specific example of the spectral characteristic of the polarization beam
splitter 12 will be described later. In addition, as a configuration of
an optical system that separates the excitation light Bs incident from
the excitation light source 11 and the emitted light from the fluorescent
member 15, it is not limited to the polarization beam splitter 12 and any
optical system may be used as long as it is configured to perform the
above-described light separating operation.

[0043] The quarter wavelength plate 13 is a phase element that generates a
phase difference of π/2 with respect to the incident light. In a case
where the incident light is linearly polarized light, the quarter
wavelength plate 13 converts the linearly polarized light to circularly
polarized light. In a case where the incident light is circularly
polarized light, the quarter wavelength plate 13 converts the circularly
polarized light to linearly polarized light. In this embodiment, the
quarter wavelength plate 13 converts a linearly polarized excitation
light emitted from the polarization beam splitter 12 to circularly
polarized excitation light and converts a circularly polarized excitation
light component included in the multiplexed light emitted from the
fluorescent member 15 to linearly polarized light.

[0044] The condensing optical system 14 condenses the excitation light
emitted from the quarter wavelength plate 13 to have a predetermined spot
diameter, and emits the condensed excitation light (hereinafter, referred
to as "condensed light") to the fluorescent member 15. In addition, the
condensing optical system 14 converts the multiplexed light emitted from
the fluorescent member 15 into parallel light and emits the parallel
light to the quarter wavelength plate 13. In addition, the condensing
optical system 14 may be configured by, for example, a single collimator
lens or may be configured to convert incident light into parallel light
by using plural lenses.

[0045] The fluorescent member 15 absorbs a part of the excitation light
(blue light) incident through the condensing optical system 14, emits
light with a predetermined wavelength band (a second wavelength) and
reflects the remainder of the excitation light. The fluorescent member 15
multiplexes the emission light and a part of the excitation light that is
reflected and emits the multiplexed light to the condensing optical
system 14.

[0046] In this example, since light incident to the optical engine section
2 is set as white light LW, the fluorescent member 15 emits light in a
wavelength band (approximately 480 to 680 nm) including red light and
green light. In this embodiment, the emission light in a wavelength band
including red light and green light and a part of the excitation light
(blue light) that is reflected by the fluorescent member 15 (a reflective
film 31 and a fluorescent layer 32 that are described later) are
multiplexed and white light is generated. In addition, a more detailed
configuration of the fluorescent member 15 will be described later.

[0047] In addition, since the emission light emitted from the fluorescent
member 15 is light that expands in a Lambertian (uniform diffusion)
shape, when the distance between the condensing optical system 14 and the
fluorescent member 15 is long, it is difficult to sufficiently condense
the emission light through the condensing optical system 14, and thereby
usage efficiency of excitation light decreases. In addition, when the
spot diameter of the excitation light emitted to the fluorescent member
15 is oversized, expansion of the emission light becomes larger and
thereby the usage efficiency decreases. Therefore, in this embodiment,
the configuration of the condensing optical system 14 such as lens
configuration, focal point distance and alignment position, and the
distance between the condensing optical system 14 and the fluorescent
member 15 are set so as to obtain sufficient usage efficiency of
excitation light.

[0048] The motor 16 rotatably drives the fluorescent member 15 for a
predetermined number of rotations. At this time, the motor 16 drives the
fluorescent member 15 so that the fluorescent member 15 rotates in a
plane (an irradiation plane of the excitation light of the fluorescent
layer 32) orthogonal to the irradiation direction of the excitation
light. Due to this, the irradiation position of the excitation light in
the fluorescent member 15 varies (moves) with the passage of time at a
speed corresponding to the number of rotations in a plane orthogonal to
the irradiation direction of the excitation light.

[0049] As described above, the fluorescent member 15 is rotatably driven
by the motor 16 and the irradiation position of the excitation light in
the fluorescent member 15 varies with the passage of time, such that it
is possible to suppress an increase in the temperature at the irradiation
position and it is possible to prevent the light emission efficiency of
the fluorescent layer 32 from being decreased. In addition, it takes some
(for example, several nsec) for fluorescent atoms to absorb the
excitation light and to emit light, and even when the next excitation
light is emitted to the fluorescent atoms for the excitation period, the
atoms do not emit light. However, according to this embodiment, the
irradiation position of the excitation light in the fluorescent member 15
varies with the passage of time, such that the fluorescent atoms not
excited are sequentially disposed at the irradiation position of the
excitation light and thereby it is possible to allow the fluorescent
layer 32 to efficiently emit light.

[0050] In addition, in this embodiment, an example where the fluorescent
member 15 is rotatably driven by the motor 16 is illustrated. However,
the invention is not limited thereto and may be configured in any manner
as long as the irradiation position of the excitation light in the
fluorescent member 15 varies with the passage of time. For example, the
irradiation position of the excitation light may vary with the passage of
time by making the fluorescent member 15 lineally reciprocate in a
predetermined direction in a plane orthogonal to the irradiation
direction of the excitation light. In addition, the irradiation position
of the excitation light may vary with the passage of time by fixing the
fluorescent member 15 and by relatively moving the excitation light
source 11 and various optical systems with respect to the fluorescent
member 15.

[3. Configuration Example of Fluorescent Member]

[0051] Next, a detailed configuration of the fluorescent member 15 will be
described with reference to FIGS. 2A to 2C. In addition, FIG. 2A shows a
front view of the fluorescent member 15 seen from the condensing optical
system 14 side, FIG. 2B shows a cross sectional view taken along a line
A-A of FIG. 2A, and FIG. 2C shows a front view of the fluorescent member
15 seen from a side opposite to the condensing optical system 14.

[0052] The fluorescent member 15 includes a disk-shaped substrate 30, a
reflective film 31 (a first reflective film) formed on one surface
(incidence side of excitation light) of the substrate 30 and the
fluorescent layer 32 (fluorescent substance).

[0053] The substrate 30 is formed from a transparent material such as
glass and transparent resin. In addition, the material for forming the
substrate 30 is not limited to a transparent material and may be formed
from any material as long as the material has a predetermined strength.
In addition, a size such as the thickness of the substrate 30 is
appropriately set in consideration of the necessary strength, weight or
the like. In addition, the center of the substrate 30 is attached to a
rotational shaft 16a of the motor 16 and the substrate 30 is fixed to the
rotational shaft 16a by a fixing hub 16b.

[0054] As shown in FIG. 2A, the reflective film 31 is formed on one
surface of the substrate 30 with a doughnut shape. The doughnut-shaped
reflective film 31 is disposed on the substrate 30 in a manner such that
the reflective film 31 and the substrate 30 are concentric to each other.
In addition, a width of the reflective film 31 in the radial direction
thereof is set to a value larger than the spot size of the excitation
light (condensed light) condensed by the condensing optical system 14.

[0055] The reflective film 31 reflects the entire light regardless of a
wavelength and an incidence angle of incident light. Therefore, the
reflective film 31 not only reflects the light (emission light) excited
at the fluorescent layer 32 to the condensing optical system 14 side, but
also reflects a part of the excitation light (blue light) transmitted
through the fluorescent layer 32 to the condensing optical system 14
side.

[0056] Here, FIG. 3 shows one configuration example of the reflective film
31. The reflective film 31 is formed by alternately laminating a first
dielectric layer 31a formed from, for example, a SiO2 layer, a
MgF2 layer or the like and a second dielectric layer 31b formed
from, for example, a TiO2 layer, a Ta2O3 layer or the like
on the substrate 30. Specifically, the reflective film 31 may be
configured by a dichroic mirror (dichroic film). In a case where the
reflective film 31 is configured by a dichroic mirror as shown in FIG. 3,
by the adjustment of a lamination count of each dielectric layer, the
thickness of each dielectric layer, a forming material of each dielectric
layer, or the like, it is possible to set a reflective (transmissive)
characteristic of the reflective layer 31 to a predetermined
characteristic. In addition, the lamination count of each of the first
dielectric layer 31a and the second dielectric layer 31b may generally be
several layers to several tens of layers. In addition, the first
dielectric layer 31a and the second dielectric layer 31b are formed by,
for example, a vapor-deposition method, a sputtering method or the like.
In addition, the configuration of the reflective film 31 is not limited
to the example shown in FIG. 3, and may be formed from, for example, a
metal film such as aluminum.

[0057] The fluorescent layer 32 may be formed from a layer-shaped
fluorescent substance, and absorbs a part of the excitation light and
emits light with a predetermined wavelength when the excitation light is
incident thereto. In addition, the fluorescent layer 32 transmits a part
of the remaining excitation light that is not absorbed and diffuses
(reflects) the remainder thereof. In addition, an excitation light
component reflected from the fluorescent layer 32 becomes non-polarized
light.

[0058] In this embodiment, a part of the excitation reflected from the
reflective film 31 and the fluorescent layer 32 and the emission light at
the fluorescent layer 32 are multiplexed and white light is generated,
such that the fluorescent layer 32 may be formed from, for example, a YAG
(Yttrium Aluminum Garnet)-based fluorescent material or the like. In this
case, the fluorescent layer 32 emits light (yellow light) with a
wavelength band of 480 to 680 nm when blue excitation light is incident
thereto.

[0059] In addition, as the fluorescent layer 32, a film of any
configuration and material may be used as long as the film can emit light
with a wavelength band including blue light and green light, and it is
preferable that a film formed from a YAG-based fluorescent material is
used, from the view point of light-emitting efficiency and heat
resistance.

[0060] The fluorescent layer 32 is formed by applying a predetermined
fluorescent agent obtained by mixing a fluorescent material and a binder
on the reflective film 31. In the example shown in FIGS. 2A to 2C, the
fluorescent layer is formed so as to cover the entire surface of the
reflective film 31, such that the surface shape of the fluorescent layer
32 become a doughnut shape. In addition, the fluorescent layer 32 may be
formed only at a region where the excitation light is emitted thereto,
such that the shape of the fluorescent layer 32 is not limited to the
example shown in FIGS. 2A to 2C, and a width of the fluorescent layer in
a radial direction may be narrower than that of the reflective film 31.

[0061] In addition, in regard to the fluorescent layer 32, the light
emission amount, and the ratio of the transmission amount to the
reflection amount (diffusion amount) of the excitation light may be
adjusted by the thickness of the fluorescent layer 32, the density
(contained amount) of the fluorescent substance, or the like. Therefore,
in this embodiment, the thickness of the fluorescent layer 32, the
density of the fluorescent substance, or the like is adjusted so that the
emitted light from the light source device section 1 becomes white light.

[0062] In addition, in the fluorescent member 15 of the above-described
embodiment, an example where the layer-shaped fluorescent substance
(fluorescent layer 32) is formed on the substrate 30 via the reflective
film 31 is described, but the invention is not limited thereto. For
example, in a case where the fluorescent substance is configured by a
plate-shaped member having a sufficient strength, the substrate 30 may be
not provided. In addition, in this case, the reflective film 31 may be
directly formed on one surface of the fluorescent substance formed from a
plate-shaped member, or a reflective mirror is prepared separately from
the fluorescent substance and the reflective mirror may be used instead
of the reflective film 31.

[4. Configuration of Polarization Beam Splitter]

[0063] In the light source device section 1 of this embodiment, as shown
in FIG. 1, an optical path of the excitation light incident to the
fluorescent member 15 from the excitation light source 11 via the
polarization beam splitter 12, and an optical path of the multiplexed
light incident to the optical engine section 2 from the fluorescent
member 15 are overlapped with each other. Therefore, in this embodiment,
as described above, a spectral characteristic of the polarization beam
splitter 12 is appropriately adjusted to separate both light beams.

[0064] FIG. 4 shows a view illustrating a spectral characteristic example
of the polarization beam splitter 12 used in this embodiment. In
addition, in the spectral characteristic shown in FIG. 4, a horizontal
axis represents a wavelength, and a vertical axis represents a
transmittance. In addition, a characteristic Tp depicted by a solid line
in FIG. 4 represents a transmittance characteristic of the polarization
beam splitter 12 with respect to P-polarized incident light, and a
characteristic Rp depicted by a broken line represents a reflectance
characteristic of the polarization beam splitter 12 with respect to
P-polarized incident light. In addition, a characteristic Ts depicted by
dotted line in FIG. 4 represents a transmittance characteristic of the
polarization beam splitter 12 with respect to S-polarized incident light,
and a characteristic Rs depicted by one-dotted line represents a
reflectance characteristic of the polarization beam splitter 12 with
respect to S-polarized incident light.

[0065] In the polarization beam splitter 12 used in this embodiment, as
shown in FIG. 4, in regard to an optical component with a wavelength band
of 480 to 680 nm that is emitted from the fluorescent layer 32, the
transmittance is approximately 100% and the reflectance is approximately
0%, regardless of a polarization direction. That is, all of the light
(yellow light) with a wavelength band of 480 to 680 nm is transmitted
through the polarization beam splitter 12.

[0066] On the other hand, as shown in FIG. 4, the transmittance of the
polarization beam splitter 12 with respect to the P-polarized blue light
is approximately 100% and the reflectance is approximately 0%. In
addition, the transmittance of the polarization beam splitter 12 with
respect to the S-polarized blue light is approximately 0% and the
reflectance is approximately 100%. That is, the polarization beam
splitter 12 transmits light when P-polarized blue light is incident
thereto, and reflects light when S-polarized blue light is incident
thereto.

[0067] By setting the spectral characteristics of the polarization beam
splitter 12 to the characteristics shown in FIG. 4, the excitation light
incident to the fluorescent member 15 and the emitted light from the
fluorescent member 15 can be separated from each other. Specifically, the
excitation light Bs (blue light) incident from the excitation light
source 11 is S-polarized light, such that it is reflected by the
polarization beam splitter 12 and is guided to the fluorescent member 15.

[0068] On the other hand, the emission light component included in the
multiplexed light emitted from the fluorescent member 15 is an optical
component with a wavelength band of 480 to 680 nm, such that it is
transmitted through the polarization beam splitter 12. In addition, in
the excitation light (blue light) components included in the multiplexed
light emitted from the fluorescent member 15, the excitation light
component reflected from the reflective film 31 is P-polarized light as
described below, such that it is transmitted through the polarization
beam splitter 12. In addition, in the excitation light components
included in the multiplexed light emitted from the fluorescent member 15,
the excitation light component directly reflected from fluorescent layer
32 is non-polarized light, such that approximately half of the excitation
light component is transmitted through the polarization beam splitter 12.
That is, a part of the multiplexed light emitted from the fluorescent
member 15 is transmitted through polarization beam splitter 12 and the
transmitted multiplexed light is guided as white light LW to the spectral
optical system 20 in the optical engine section 2.

[5. Operation Example of Light Source Device Section]

[0069] Next, an operation example of a light source device section of this
embodiment will be described in detail with reference to FIGS. 1 to 5. In
addition, FIG. 5 shows a view illustrating a state of an operation of the
polarization beam splitter 12 of this embodiment. In FIG. 5, the circle
A1 represents an S-polarization direction and the white arrow A2
represents a P-polarization direction. In addition, in FIG. 5, for
simplicity of description, a non-polarized excitation light component
directly reflected from the fluorescent layer 32 is not shown.

[0071] Subsequently, when the excitation light is emitted to the
fluorescent layer 32 of the fluorescent member 15, the fluorescent layer
32 absorbs a part of the excited light and thereby emits light (yellow
light) with a wavelength band of 480 to 680 nm including red light and
green light. In addition, at this time, the fluorescent layer 32 diffuses
a part of the excitation light that is not absorbed at the fluorescent
layer 32 side and reflects it to the condensing optical system 14 side,
and transmits a part of the remaining excitation light that is not
absorbed and guides it the reflective film 31. The reflective film 31
reflects the excitation light that is transmitted through the fluorescent
layer 32 to the condensing optical system 14 side. In addition, at this
time, a part of the emission light of the fluorescent layer 32 is
reflected from the reflective film 31 to the condensing optical system 14
side.

[0072] As a result, the emission light from the fluorescent layer 32 and a
part of the excitation light reflected from the fluorescent layer 32 and
reflective film 31 are multiplexed in the fluorescent member 15, and the
multiplexed light is emitted from the fluorescent member 15 to the
condensing optical system 14.

[0073] Subsequently, the condensing optical system 14 converts the
multiplexed light emitted from the fluorescent member 15 into parallel
light and emits the parallel light to the polarization beam splitter 12
via the quarter wavelength plate 13.

[0074] At this time, a light component included in the multiplexed light
that passes through the quarter wavelength plate 13, that is, a red light
component Rps (broken line arrow in FIG. 5) and a green light component
Gps (one-dotted line arrow) are non-polarized light (including a
P-polarized component and a S-Polarized light component). Therefore, the
red light component Rps and green light component Gps included in the
multiplexed light transmit through the quarter wavelength plate 13 "as
is" and are incident to the polarization beam splitter 12.

[0075] On the other hand, in the excitation light component (blue light
component) included in the multiplexed light, the excitation light
component reflected from the reflective film 31 passes through the
quarter wavelength plate 13 a total of two times until it is incident to
the polarization beam splitter 12. Specifically, the excitation light
component reflected from the reflective film 31 passes through,
respectively, the quarter wavelength plate 13 in an optical path from the
excitation light source 11 to the fluorescent member 15 and the optical
path from the fluorescent member 15 to the polarization beam splitter 12
one at a time. Therefore, a polarization direction of the reflected light
component from the reflective film 31, which is included in the
multiplexed light after passing through the quarter wavelength plate 13,
is rotated by 90° with respect to the excitation light Bs emitted
from the excitation light source 11.

[0076] In this embodiment, the excitation light Bs emitted from the
excitation light source 11 is S-polarized light, such that the excitation
light component Bp (blue light) incident to the polarization beam
splitter 12 after being reflected from the reflective film 31 becomes
P-polarized light as shown in FIG. 5. On the other hand, since the
excitation light component (not shown in FIG. 5) directly reflected from
the fluorescent layer 32 is non-polarized light, it passes through the
quarter wavelength plate 13 "as is", and is incident to the polarization
beam splitter 12 (not shown in FIG. 5).

[0077] In addition, in this embodiment, the polarization beam splitter 12
is made to have a spectral characteristic as shown in FIG. 4, such that
the polarization beam splitter 12 passes the red light component Rps and
the green light component Gps included in the multiplexed light "as is".

[0078] In addition, in the excitation light components incident to the
polarization beam splitter 12, the reflected light component (Bp) from
the reflective film 31 is P-polarized light, such that the polarization
beam splitter 12 passes the reflected light component (Bp) from the
reflective film 31 "as is". Therefore, in the excitation light components
incident to the polarization beam splitter 12, the reflected light
component from the fluorescent layer 32 is non-polarized light, such that
the polarization beam splitter 12 passes only the P-polarized light in
the reflected light components. At this time, in the excitation light
components reflected from the fluorescent layer 32, the ratio of
component passing through the polarization beam splitter 12 is
approximately 50%. Therefore, in this embodiment, in the excitation light
component emitted from the fluorescent member 15, an excitation light
component of approximately 70 to 80% passes through the polarization beam
splitter 12.

[0079] As a result, light obtained by multiplexing the red light component
Rps, the green light component Gps, and a part of excitation light
component (blue light component) reflected from the reflective film 31
and the fluorescent layer 32, that is, white light LW is emitted from a
light emitting surface, which is located at the optical engine section 2
side, of the polarization beam splitter 12. In this embodiment, the white
light LW is emitted from the light source device section 1 as described
above.

[0080] In regard to the light source device section 1 having the
above-described configuration of this embodiment, the present inventor
set parameters of each portion of the light source device section 1 as
described below and examined spectral characteristics of emitted light
from the light source device section 1. [0081] Wavelength of the
excitation light source 11 (blue laser) : 445 nm [0082] Condensing
diameter of excitation light: 1 mm [0083] Incidence angle θ of
excitation light: 20° or less [0084] Spectral characteristics of
the polarization beam splitter 12: a characteristic shown in FIG. 4
[0085] Distance between the condensing optical system 14 and the
fluorescent layer 32: 1 mm or less [0086] Number of rotations of the
fluorescent member 15: 3000 rpm [0087] Forming material of the
fluorescent layer 32: A YAG-based fluorescent substance [0088] Thickness
of the fluorescent layer 32: 50 μm [0089] Width of the fluorescent
layer 32: 5 mm

[0090] FIG. 6 shows a spectral characteristic of an emitted light from the
light source device section 1, which is obtained under the
above-described condition. In addition, in the characteristic shown in
FIG. 6, a horizontal axis represents a wavelength, and a vertical axis
represents intensity (any unit) of the emitted light. As can be seen from
FIG. 6, under the conditions, it can be seen that a light component (blue
light component) near a wavelength of 445 nm and a light component with a
wavelength ranging from approximately 480 to 680 nm, that is, a light
component including a red light component and a green light component are
included in the emitted light. From this, it can be seen that white light
is emitted from the light source device section 1 of this embodiment.

[0091] As described above, it is possible to emit the white light from
light source device section 1 by using a solid-state light emitting
device. Therefore, this embodiment may be applied for application where a
light source device emitting white light is necessary, for example, like
in a 3 LCD type projector. That is, in this embodiment, it is possible to
provide a mercury-free light source device section (illumination device),
which can be applied for various applications, and an image display
apparatus 10 having the same.

[0092] In the light source device section 1 of this embodiment, it is not
necessary to use a mercury lamp, such that it is possible to cope with a
recent environmental problem. In addition, according to this embodiment,
it is possible to provide a light source device section 1 of which
durability is longer and decrease in brightness is also lower compared to
the mercury lamp, and an image display apparatus 10. In addition, like in
this embodiment, when a solid-state light emitting device is used in the
excitation light source device section 11, a lighting time may be
shortened compared to the mercury lamp.

[0093] In addition, in a case where a semiconductor laser is used as the
excitation light source 11 like in the light source device section 1 of
this embodiment, light with a sufficiently high brightness may be emitted
compared to a solid-state light source such as an LED (Light Emitting
Diode) and thereby it is possible to realize a high brightness light
source. In addition, like in this embodiment, a configuration where the
fluorescent layer 32 is made to emit light by using a blue light laser to
generate white light is simpler and cheaper than a configuration where
solid-state light sources for red light, green light, and blue light are
separately prepared to generate white light.

[6. Various Modified Examples]

(1) Modified Example 1

[0094] In this embodiment, there is described an example where excitation
light incident to the fluorescent member 15 and white light are separated
by using the polarization beam splitter 12, but the invention is not
limited thereto. For example, a reflective mirror, which is configured to
reflect blue light at some regions, may be used instead of the
polarization beam splitter 12. An example thereof (modified example 1) is
shown in FIG. 7.

[0095] A reflective mirror 40 (spectral optical system) of modified
example 1 includes a plate-shaped transparent substrate 41 (base) and a
reflective film 42 (second reflective film) that is formed one surface of
the transparent substrate 41. The reflective film 42 is formed with a
size approximately equal to the spot diameter of excitation light. In
addition, in this example, the reflective film 42 is disposed at an
irradiation position of the excitation light and the reflective mirror 40
is disposed inside of the light source device section 1 in a manner that
a surface of the reflective mirror 40 is slanted approximately 45°
with respect to an incidence direction of excitation light.

[0096] The transparent substrate 41 is formed from, for example, a glass
or a transparent material such as a transparent resin, and the reflective
film 42 may be configured by, for example, a dichroic mirror (dichroic
film) shown in FIG. 3. In a case where the reflective film 42 is
configured by the dichroic mirror, by adjusting a forming material of
each dielectric layer and a thickness of the dielectric layer and a
lamination count, or the like, it is possible to selectively reflect blue
light and transmit another wavelength component. In addition, the
reflective film 42 may be formed from a metal film such as aluminum.

[0097] In a case where the reflective mirror 40 having a configuration
shown in FIG. 7 is used, excitation light from the excitation light
source 11 is reflected from the reflective film 42 and is incident to the
fluorescent member 15. On the other hand, multiplexed light (white light
LW), which is incident to the reflective mirror 40 from the fluorescent
member 15 via condensing optical system 14, mainly passes through a
region where the reflective film 42 is not formed and is incident to the
optical engine section 2. In addition, in a case where the reflective
film 42 is designed to transmit light with a wavelength band other than
blue light, red light component and green light component included in the
multiplexed light (white light LW) also pass through the region where the
reflective film 42 is formed.

[0098] In this example, in a case where a semiconductor laser is used as
the excitation light source 11, the spot diameter of excitation light
emitted from the excitation light source 11 is sufficiently smaller than
that of each multiplexed light (white light LW) emitted from the
condensing optical system 14. Therefore, it is also possible to emit
white light LW with a sufficiently large strength from the light source
device section 1 in the configuration of this example.

[0099] In addition, like in this example, in a case where the reflective
mirror 40 is used as a spectral optical system for separating the
excitation light incident to the fluorescent member 15 and the
multiplexed light incident to the optical engine section 2, it is
possible to make the configuration of the spectral optical system
simpler. In the configuration of this example, since it is not necessary
to consider a polarization direction of light incident to reflective
mirror 40, it is not necessary to provide the quarter wavelength plate 13
like in the embodiment. Therefore, in this example, it is possible to
make the configuration of the light source device section 1 simple and it
is possible to provide a cheap light source device section 1.

(2) Modified Example 2

[0100] In the embodiment and modified example 1, there is described an
example where the spectral optical system (polarization beam splitter 12
or reflective mirror 40) reflects the excitation light emitted from the
excitation light source 11 and transmits the multiplexed light emitted
from the fluorescent member 15. However, the invention is not limited
thereto.

[0101] For example, the spectral optical system may be configured to
transmit the excitation light emitted from the excitation light source
11, guide it the fluorescent member 15, reflect the multiplexed light
emitted from the fluorescent member 15 and guide it the optical engine
section 2. In addition, in this case, the excitation light incident to
the polarization beam splitter 12 from the excitation light source 11 is
set as P-polarized light.

(3) Modified Example 3

[0102] In the embodiment, there is described an example where the quarter
wavelength plate 13 is provided in the light source device section 1, but
the invention is not limited thereto. For example, in a usage where white
light with a high output is not necessary, the quarter wavelength plate
13 may be not provided.

[0103] In a case where the quarter wavelength plate 13 is not provided,
the S-polarized excitation light is directly incident to the fluorescent
layer 32 via the polarization beam splitter 12 and the condensing optical
system 14. In this case, a part of the excitation light incident to the
fluorescent layer 32 diffuses in the fluorescent layer 32 and a
non-polarized excitation light component is reflected to the condensing
optical system 14. In the excitation light components reflected from the
fluorescent layer 32, only P-polarized light component is transmitted
through the polarization beam splitter 12. In addition, the excitation
light component reflected from the reflective film 31 is S-polarized
light, the excitation light component does not transmit through the
polarization beam splitter 12. Therefore, in the configuration of this
example, white light including the P-polarized light component of the
excitation light reflected from the fluorescent layer 32 and emission
light from the fluorescent layer 32 is emitted from the light source
device section 1.

[0104] In addition, in the configuration of this example, the excitation
light component included in the white light (multiplexed light) emitted
from the light source device section 1 includes only the P-polarized
light component reflected from the fluorescent layer 32. Therefore, in
this example, the intensity of the emitted light and the usage efficiency
of excitation light decrease compared to the embodiment. However, in the
light source device section 1 of this example, it is not necessary to
provide the quarter wavelength plate 13, such that the configuration
thereof becomes relatively simple compared to the embodiment.

(4) Modified Example 4

[0105] In the embodiment and the modified example 1, there is described an
example where the excitation light incident to the fluorescent member 15
and the multiplexed light emitted from the fluorescent member 15 are
separated by using the spectral optical system (the polarization beam
splitter 12 or the reflective mirror 40), but the invention is not
limited thereto. For example, in a case where the excitation light is
incident obliquely with respect to the fluorescent member 15 and the
multiplexed light emitted from the fluorescent member 15 is condensed in
an optical path different from that of the excitation light, the
above-described spectral optical system and quarter wavelength plate 13
may be not provided. In this case, the configuration of the light source
device section 1 becomes relatively simple.

(5) Modified Example 5

[0106] In the embodiment, there is described an example where the
condensing optical system 14 is provided in the light source device
section 1, but the invention is not limited thereto. For example, in a
case where the light source device section 1 of the embodiment is applied
for a usage where white light with a high output is not necessary, the
light source device section 1 may be configured so as not to include the
condensing optical system 14.

(6) Modified Example 6

[0107] In the embodiment, there is described an example where the emitted
light of the light source device section 1 (illumination device) is set
as white light, but the invention is not limited thereto. For example, as
the emitted light, blue light may be used for a usage where cyan light
(or magenta light) is necessary as the excitation light, or the
fluorescent layer 32 may be formed by a fluorescent material that emits
only green light (or red light). That is, according to a necessary
wavelength (color) of the emitted light, a combination of the wavelength
of the excitation light and the material for forming the fluorescent
layer 32 may be appropriately selected. In this case, an applicable usage
range may be more extendable.

[0108] It should be understood by those skilled in the art that various
modifications, combinations, sub-combinations and alterations may occur
depending on design requirements and other factors insofar as they are
within the scope of the appended claims or the equivalents thereof.